I'm a mere 57, but I've hiked extensively with some close friends who are over 60, a couple of guys in particular. These are guys that I met while thru-hiking the PCT. They were doing so too. One had just had double hernia surgery, but was on trail doing big miles. He went on to hike the CDT the next year, at age 65 or so I think. I hiked the majority of the Appalachian Trail with the other one.

My point here is that folks over 60 can do very extensive backpacking journeys. Certainly a degree of living sensibly prior and good genetics and good fortune all come into play. As does a modicum of backpacking experience and wisdom. And just a strong enough desire to keep getting out there.

I've run into a couple of spry 70+ years olds on trail, but definitely less of those. I'm hoping to be one of them, but time will tell!
Brian Lewis